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Re: Quasars And Blackholes

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Posted by Joe Postma/">Joe Postma on March 14, 1998 17:23:04 UTC

Hello Imran, Pulsars and quasars are very different objects. Pulsars are one possible end stage in the lifetime of a star. When some stars which are massfull enough run out of fuel the stars core can no longer produce enough energy to counteract the inward pull of gravity. This results in the stars core colapsing in on itself and will cause what is known as a supernova-the outer regions of the star are litterally blown apart into space. The core of the star which collapsed in on itself remains however, and if the conditions were right at the outset (ie-the core had sufficient mass) the atomic strucure of the core will not even be able to support itself against the force of gravity and the atomic structure of the core will itself break down. All the atoms making up the core are squashed into eachother, causing all the protons making up the atoms to disintigrate, or to collapse, therebye being transformed into neutrons and positrons. The only thing that is left of the core is an ultra dense sea of neutrons and electrons, wieghing perhaps billions of tons per cubic cenimeter. This state is called a neutron star, and the only thing that stops the core from collapsing any further is the subatomic structure of the neutrons themsleves. So then, the resulting neutron star has a diameter of only a few kilometers, but it still posesses certain attributes of the original star such as its spin. You've probably heard of the analogy of a spinning skater who pulls in her arms thus causing her to spin faster than if she held her arms out from her, the same is true for the neutron star. The original stars spin is passed down to the neutron star; since the neutron star is many many times smaller than the original star, this causes the neutron star to spin on its axis very very quickly. Some neutron stars are observed to spin thousands of times on their axis every second. This spinning causes very powerful magnetic feilds to be produced, and due to the physical mechanics involved, will form highly focused beams of radio waves and other electromagnetic spectra to be emmitted. Sometimes these beams sweep past the Earth, and appear to astronomers like a cosmoc lighthouse. The resultant blinking has led astronomers to call these pulsars. One more thing, pulsars are found inside our galaxy, at intersteller distances(measured in thousands of light years), rather than existing outside at cosmological distances. Quasars on the other hand are found at cosmological distances, distances which are measured in the billions of light years away. Quasars are thought to be the active core of very young galxies-more specifically, are thought to be the massive black holes around which galaxies form. Quasars and black holes do indeed exhibit the same characteristics, that is because they are the same thing-except that they are very massive black holes, with masses measured in the millions and even billions of solar masses.

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